Radioactive isotope adsorption

Hydrochloric Acid on Alumina, 1128 Radioactive Isotope Adsorption, 1128 Adsorption of iron and Nickei Carbonyis, 1128... 

Until the advent of modem physical methods for surface studies and computer control of experiments, our knowledge of electrode processes was derived mostly from electrochemical measurements (Chapter 12). By clever use of these measurements, together with electrocapillary studies, it was possible to derive considerable information on processes in the inner Helmholtz plane. Other important tools were the use of radioactive isotopes to study adsorption processes and the derivation of mechanisms for hydrogen evolution from isotope separation factors. Early on, extensive use was made of optical microscopy and X-ray diffraction (XRD) in the study of electrocrystallization of metals. In the past 30 years enormous progress has been made in the development and application of new physical methods for study of electrode processes at the molecular and atomic level. 

To resolve the problem applying methods of collimated atom beams, equilibrium vapour as well as radioactive isotopes, the Hall effect and measurement of conductivity in thin layers of semiconductor-adsorbents using adsorption of atoms of silver and sodium as an example the relationship between the number of Ag-atoms adsorbed on a film of zinc oxide and the increase in concentration of current carriers in the film caused by a partial ionization of atoms in adsorbed layer were examined. 

Although radioactive isotopes have been widely utilized as tracers in the study of adsorption equilibrium and kinetics, in these types of studies they provide no direct information on chemical structure... 

Precipitation of Hafnium Hydroxide. In order to interpret the adsorption data it was necessary to determine the conditions which lead to the precipitation of hafnium hydroxide. It is not usually advisable to depend on the solubility product because the information on this quantity is often unreliable for hydroxides of polyvalent metal ions. In addition, "radiocolloids may apparently form much below saturation conditions in radioactive isotope solutions. In the specific case of hafnium hydroxide only two measurements of the solubility seem to have been reported. According to Larson and Gammill (16) K8 = [Hf(OH)22+] [OH ]2 — 4 X 10"26 assuming the existence of only one hydrolyzed species Hf(OH)22+. The second reported value is Kso = [Hf4+] [OH-]4 = 3.7 X 10 55 (15). If one uses the solubility data by Larson and Gammill (Ref. 16, Tables I and III) and takes into consideration all monomeric hafnium species (23) a KBO value of 4 X 10 58 is calculated. 

Sr is one of the most hazardous and dangerous radioactive isotopes. It is a pure beta emitter (Eimj = 546 keV) and decays to another pure beta emitter, 90Y ( max = 2283.9 keV).10 The radiochemical methods for determining 90Sr in aquatic samples (water, sediment, and biota) are based on the adsorption of radiostrontium on AMP in water samples, mineralization of sediment and biota, and sorption on Sr resin.14 16... 

The phenomenon of very diluted solutions is well known in radiochemistry. Carrier-free radioactive isotopes could be mentioned as an example. The term denotes a radioisotope of an element in pure form, that is, essentially undiluted, with a stable isotope. The chemical concentration of these radioisotopes is usually very low. For example, 1 kBq radioactivity (applied typically in a tracer experiment) is equivalent to cca. 2 10 12 mol in the case of 137Cs or 90Sr isotopes. In the case of such low concentrations, no chemical system can be considered homogeneous because all surfaces, the wall of the laboratory vessels, or any contaminants in the solution (such as air bubbles, small particles, great molecules, etc.) can initiate interfacial processes and the subsequent formation of heterogeneous phases (adsorption, colloid formation, precipitation, etc.). This is the result of the simple fact that the number of molecules on the surfaces is more than, or at least similar to, the number of particles in the solution. Even in a solution containing... 

The results of investigations of adsorption and desorption of tin and palladium ions obtained by the methods of radioactive isotopes, XPS and photometry under different experimental conditions (1-4, 13, 15, 18, 25, 30). The glass and quartz plates were immersed into the solution containing 113 Sn and 103 Pd radioactive isotopes introduced as chlorides. 

Another difficulty is that only a small part of problem waste contains cations or well sorbed matter. Reactor waste often contains radioactive isotopes in the form of anions, which in substance are not adsorbed. In waste waters of chemical factories is also present unabsorbable matter and also ligands, which may form with cations complex compounds strongly degrading cation adsorption. One more consequence of adsorption and retardation is that a water horizon contaminated with adsorbed matter is very difficult to clean up and remove pollutants from it. 

Krishnaswami S, Graustein WC, Turekian KK, Dowd F (1982) Radium, thorium, and radioactive lead isotopes in groundwaters application to the in-situ determination of adsorption-desorption rate constants and retardation factors. Water Resour Res 6 1663-1675 Krishnaswami S, Bhushan R, Baskaran M (1991) Radium isotopes and Rn in shallow brines, Kharaghoda (India). Chem Geol (Isot Geosci) 87 125-136 Kronfeld J, Vogel JC, Talma AS (1994) A new explanation for extreme " U/ U disequilibria in a dolomitic aquifer. Earth Planet Sci Lett 123 81-93... 

Manheim FX, Pauli, CK (1981) Patterns of ground water salinity changes in a deep continental-oceanic transect off the southeastern Atlantic coast of the U.S.A. J Hydrol 54 95-105 Martin P, Akber RA (1999) Radium isotopes as indicators of adsorption-desorption interactions and barite formation in groundwater. J Environ Radioact 46 271-286 McCarthy J, Shevenell L (1998) Obtaining representative ground water samples in a fractured and karstic formation. Ground Water 36 251-260... 

That z actually is an adsorption coefficient has been demonstrated by Balandin et al. (19). A mixture of butane and butylene was dehydrogenated, one of the compounds being labeled with the radioactive C14 isotope. It was found that in the consecutive reaction... 

Radium may be transported in the atmosphere in association with particulate matter. It exists primarily as a divalent ion in water, and its concentration is usually controlled by adsorption-desorption mechanisms at solid-liquid interfaces and by the solubility of radium-containing minerals. Radium does not degrade in water other than by radioactive decay at rates that are specific to each isotope. Radium may be readily adsorbed by earth materials consequently, it is usually not a mobile constituent in the environment. It may be bioconcentrated and bioaccumulated by plants and animals, and it is transferred in food chains from lower trophic levels to humans. 

The adsorption of Cd(II) and oxalate or citrate ions was calculated from an uptake of their concentration from solution. The ion concentration in solution was determined by the radiotracer method. For labelling the solution, 14C or 115Cd isotopes were used. Radioactivity of the solutions before and after adsorption was measured using a liquid scintillation counter (LS5000 TD Beckmann). Co-adsoprtion of Cd(II) and carboxylate ions was determined simultaneously. The adsorption of measured ions was conducted in a pH range from 3.0 to 10.0. 

There is nothing new in principle about the use of isotopes as an aid to chemistry. For twenty years the radioactive elements have been used as indicators to study adsorption, solubility, volatility, distribution, and other phenomena of physical chemistry. Distribution of heavy radioactive atoms in plants has been studied through the relative amount of ionization found in the different parts. The ionization theory was supported by dissolving radioactive lead chloride in an aqueous solution of ordinary lead nitrate and then crystallizing out the lead chloride. The radioactive lead was found to be equally distributed between the two salts. In aqueous solution the two different kinds of lead are free to exchange anions, as predicted from the electrolytic dissociation theory. With un-ionized compounds of lead it was found that exchange does not take place. 

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